FIVE DAYS; A TRIO OF INVESTMENTS

By MICHAEL J. de la MERCED

Published: May 19, 2007

Billionaire investors helped drive the markets higher as they unveiled major stakes in a bevy of companies.

On Wednesday, an affiliate company of Edward S. Lampert, the hedge fund manager, reported in a regulatory filing that it had bought more than 15 million shares in Citigroup, a purchase worth almost $800 million. That same day, Berkshire Hathaway, run by Warren E. Buffett, revealed in a filing that it had raised its railroad holdings, disclosing that it had acquired stakes in Norfolk Southern and Union Pacific worth a combined $1.4 billion. And on Thursday, an affiliate company of Carl C. Icahn, the activist investor, reported that as of March 31, he held a $122 million stake in another railroad company, CSX.

While the antipodal investment philosophies of Mr. Buffett and Mr. Icahn are well known, Mr. Lampert's motivation in buying the Citigroup stake remains unknown. It is possible that he may simply find the troubled financial giant's stock undervalued or that he may agitate for change at the top. MICHAEL J. de la MERCED